A. Field of Invention
This invention pertains to an ultrasonic scanner incorporating a linear scanning device, and more particularly, a scanning device with a hybrid analog-digital controller incorporating a Hall effect device as a feedback or position sensor and a DC motor.
B. Description of the Prior Art
Many electronic instruments include an element or component that is moved or positioned very accurately in order to insure that a desired parameter is measured properly, that a mechanical or electromagnetic force is applied at a desired location or that a physical phenomenon is measured properly. For example, ultrasonic scanner devices typically include an ultrasonic transducer that directs an ultrasonic beam at biological tissues or other samples of interest and a detector that detects the ultrasonic beam reflected from various layers within the tissues or samples. The resulting signals are then analyzed and information is produced about various aspects of the tissues, or sample, such as, for example, their internal structure. Normally, information is sought for not just a single point within the tissues but with regard to a whole area or zone. In order to obtain this information, it is necessary to move the transducer and the detector by a predetermined distance. Often in such a situation, a scanning operation is performed wherein a signal is obtained when the transducer and the detector are at a predetermined location, the transducer and detector are moved by a small amount and a new signal is obtained. This process can be repeated numerous times until the whole area or zone of interest within the tissue or sample has been scanned.
There are many prior art scanners that obtain information about tissue structures and other similar information by using the scanning operation described above. The scanning operation could be accomplished using either analog or digital techniques. Purely analog techniques may not be ideal for this type of operation because they may not be accurate enough, especially if the incremental movement required is very small. That is why existing devices (such as the transducers available from Capistrano Labs, Inc., San Clemente, Calif. 92672) use a digital scheme requiring stepping motors, digital resolvers and other expensive and complicated precision components.
The present inventor has discovered that this problem is solved by using a hybrid analog/digital control scheme, as described below.